From the field of conservation agents for metal and coated surfaces for example it has been known for a long time to prepare aqueous dispersions in a process free from solvent, so only using water. For example U.S. Pat. No. 4,693,909 discloses a liquid preservative for plated or unplated metal surfaces and surfaces of coatings, in the form of an aqueous wax dispersion which contains a special ethylene/acrylic acid copolymer wax, consisting of from 8 to 25% by weight of acrylic acid units and from 92 to 75% by weight of ethylene units, in partially or completely neutralized form, if appropriate as a mixture with waxes based on polyethylene oxidation products and/or hydrocarbon waxes, the use of this special ethylene/acrylic acid copolymer wax for preserving plated or unplated metal surfaces and surfaces of coatings, and a process for temporarily preserving metal surfaces and surfaces of coatings. The dispersion is produced in that an ethylene/acrylic acid copolymer wax (referred to as EAA wax) as a starting material, frequently in the form of granules, is emulsified with the required amount of water and the appropriate amount of a base in an emulsification autoclave under from 4 to 6 bar and at from 140° C. to 160° C., while stirring.
More specific processes of this kind which are allegedly more efficient or lead to small size particle stable dispersions or which are based on different starting materials are disclosed in a number of documents such as for example U.S. Pat. Nos. 5,387,635, 5,206,279, WO 98/06774, or US 2004/0029977. WO2007/110417 specifically discloses a process for the preparation of an aqueous rubber emulsion (artificial latex), comprising the steps: (a) size reduction of the rubber, whereby granules are produced with shorter dissolving time; (b) cement formation, wherein the granules of step (a) are dissolved in a suitable hydrocarbon solvent; (c) preparation of an aqueous soap solution; (d) emulsification of the cement formed in step (b), using the aqueous soap solution prepared in step (c), thus forming an oil in water emulsion; (e) hydrocarbon solvent removal, resulting in an aqueous emulsion of the rubber, and optionally (f) emulsion concentration, forming an artificial latex with a higher solids content, wherein in step (a) the size reduction is carried out using a to chopper and/or granulator characterized in that a soap is used as processing aid, preferably identical to the soap used in steps (c) and (d).
As concerns the practical realisation for carrying out such a process, EP 173 456 proposes a process in which a hydrophobic thermoplastic resin such as an olefin resin and a water-insoluble or non-water-swelling polymer containing a carboxylic acid salt group are melt-kneaded in the presence of water and phase inversion occurs to form a dispersion comprising resin particles dispersed in water, even if the amount of water is very small. If an anionic surfactant, optionally together with a solvent or oil, is included, the size of the dispersed resin particles can be greatly reduced even if a resin having a very high molecular weight or a high melt viscosity is used. In this document it is proposed to carry out the process either using a kneader, a Banbury mixer or a multi-shaft screw extruder.
Similar continuous methods using extruders are disclosed in EP 359045, DE 10109992, as well as WO 2005/021638.